cooling system weirdness - air pocket?

[guidos]

Hey All.

Put a new thermostat, radiator hoses, and coolant into a VL turbo the other day. The lower bleed bolt snapped while trying to undo it, so i bled it by taking out the temperature sender which is next to it. I then bled using the bolt on the top of the plenum, as normal.

I havent had the car long and before this the thermostat was stuck open, so it would barely warm up.

Now with the new thermostat, it warms up to the correct temp, but after driving a while and shutting the engine off, you can hear what sounds like water dripping or bubbling somewhere to the rear of the motor. There is almost no pressure in the system (i can squeeze the radiator hose and make both sides touch). I took the radiator cap off, and the water level was going up and down over and over again, like you were squeezing a hose and letting go and repeating that.

Now before someone screams cracked head.. the oil and water arent contaminated, and the compression is what it should be, and im not losing any water.

There is a *very slight* leak (small enough to not even see the level change) from a heater hose by the look of it, and since the inlet manifold is off this weekend i'll change that.

Any ideas as to whats going on?

I'm thinking maybe that bleeding the lower half through the temp sender somehow still left some air in there. I'll be getting the snapped bolt changed soon hopefully (easy out broke trying to take it out!) or a new lower half of the manifold, and changing the heater hose.

Any ideas?

[Jim]

did you turn the heater tap on when you warmed the car up, with the rad cap off? it might be air blocked in the heater core.

[guidos]

sorry yes i did :)

i should add this is the 4th vl i've owned and probably like the 100th time i've bled a cooling sytem and i've never seen this before... thats why im so confused!

[tweak]

the bubbling noise you hear is the water boiling in the heater hoses running into the firewall.
happen's to both the vlt's ive owned and is apparantly a common occurence and nothing to worry about.
not sure why there is no pressure though.

[guidos]

hmm well i just looked through my holden book, the turbo happens to get its water from the block, and dump it into where the output pipe from the heater goes to. this could explain the boiling down there after taking it for a bit of a spin on boost... but still, it should boil if its under pressure, should it?

[tandy ass]

I've had the same problem in numerous RB30's I've owned as well, tweak is right that its a boiling water in some point thats causing it to go up and down.

In the VL the symptoms are much worse because of the lower radiator position, the best method I found to bleed a VL's cooling system was to get a 2L coke bottle and cut the bottom out of it and wedge it into the radiator filler, my radiator was just the right size to be able to screw it into place.

Now open the TOP bleeder (on top of the plenum) and put the heater on hot with a hose slowly trickling water into the coke bottle (this raises the fill point. Start the engine and let it idle for about 30 minutes, while the hose is running and the water is to the top of the coke bottle.

Perfect VL bleeds every time :)

[guidos]

yes bozz i used to do it that way, i still use the coke bottle but my method is to undo both bleeders, fill with the coke bottle till it comes from the lower one, then put the lower bleed in and the radiator cap on, and use a hose attached to the radiator overflow hose to fill it until i get water coming out of the top bleed hose.

all i can presume is that there is a leak that let some water in somewhere, or the heater slider is disconnected (possibility since i never actually used it!). i'm putting all new heater hoses on and i'll flush the heater to be sure, hopefully it'll all be ok after this.

thanks for the help people.

[guidos]

head ended up being cracked. 9" long crack on exhaust side from cyls 6-3. looks like the head has been done before, as a non nissan gasket was installed. also the water jackets where the crack was seemed to be blocked by what looked like water pump or thermostat gasket pieces. there was also corrosion on some of the water jackets so i got a secondhand head and had that reco'd. should have it running again monday, so fingers crossed its all alright.

thankfully the bottom end looks fine though, but i guess thats no suprise for a stock RB30.